The present invention relates to a master cylinder, in particular for a hydraulic automotive vehicle brake system.
A master cylinder of this type is disclosed in U.S. Pat. No. 5,187,934. To ensure pressure compensation between the pressure chamber and the supply chamber and the function of replenishment from the supply chamber into the pressure chamber, pressure compensation ports configured as bores are provided in the pistons of the prior art master cylinder which are designed as plungers. The bores are adequate for pressure compensation and for the protection of the replenishment action during bleeding of the brake system. However, when the master cylinder is intended for use in brake systems with traction slip control, driving dynamics control or other independently operable brake systems, a small number of bores are not sufficient to furnish the fluid flow which is required by the pump of the brake system. The small cross-section of the bores produces an excessive throttling resistance, with the result that the fluid volume required in the independently controlled braking mode (for example, traction slip control or driving dynamics control) cannot be made available in a sufficiently short time. The provision of a larger number of bores increases the manufacturing costs and, thus, is uneconomical.
An object of the present invention is to overcome the problem mentioned with respect to the state of the art without unreasonably increasing the manufacturing costs.